libvirt-guests: Remove LISTFILE if it's empty when stopping service

$LISTFILE is created even no domain is running, and the empty
$LISTFILE could cause improper service status.

    stopped ,with saved guests

Which is not right, as there is no domain was saved.

tools/libvirt-guests.init.sh

@@ -461,6 +461,7 @@ stop() {
     done
     set +f
 
+    if [ -s "$LISTFILE" ]; then
         while read uri list; do
             if "$suspending"; then
                 eval_gettext "Suspending guests on \$uri URI..."; echo
@@ -481,6 +482,9 @@ stop() {
                 done
             fi
         done <"$LISTFILE"
+    else
+        rm -f "$LISTFILE"
+    fi
 
     rm -f "$VAR_SUBSYS_LIBVIRT_GUESTS"
 }